Reagent channel mixing system and method

ABSTRACT

An analysis system may perform operations on an analyte that may be combined with multiple regents prior to being introduced into a flow cell. The instrument may include a volume into which the reagents to be combined with the analyte are aspirated one-by-one. The volume may be formed as a serpentine channel in a valve manifold associated with sippers for aspirating the reagents. The reagents may then be mixed by cycling a pump to move the reagents within the mixing volume or channel. For this, the reagents may be aspirated from a recipient into the volume or channel, ejected back into the recipient, and this process may be performed repeatedly to enhance mixing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application under 35 U.S.C. § 120 ofU.S. patent application Ser. No. 15/841,102, filed Dec. 13, 2017, whichclaims benefit of priority to British (GB) Patent Application No.1704758.0, filed Mar. 24, 2017, which claims benefit of priority to U.S.Patent Application No. 62/442,772, filed Jan. 5, 2017, as well asbenefit of priority under 35 U.S.C. § 119(e) to U.S. Patent ApplicationNo. 62/442,772, filed Jan. 5, 2017, all of which are hereby incorporatedby reference herein in their entireties.

BACKGROUND

Instruments have been developed and continue to evolve for sequencingmolecules of interest, particularly DNA, RNA and other biologicalsamples. In advance of sequencing operations, samples of the moleculesof interest are prepared in order to form a library or template whichwill be mixed with reagents and ultimately introduced into a flow cellwhere individual molecules will attach at sites and be amplified toenhance detectability. The sequencing operation, then, includesrepeating a cycle of steps to bind the molecules at the sites, tag thebound components, image the components at the sites, and process theresulting image data.

In such sequencing systems, fluidic systems (or subsystems) provide theflow of substances (e.g., the reagents) under the control of a controlsystem, such as a programmed computer and appropriate interfaces.

SUMMARY

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims.

In some implementations, a system may be provided that includes a flowpath to be fluidically connected with a flow cell to support analytes ofinterest in an analysis system. The system may further include aselector valve fluidically coupled to the flow paths to select between aplurality of reagent sippers for an analysis operation, a bypass linethat is separate from the flow path and for which a portion of thebypass line serves as a mixing volume, a pump to be fluidicallyconnected with the bypass line and to displace fluids through the bypassline during a reagent pre-mixing operation, and control circuitryoperatively coupled to the selector valve and to the pump, the controlcircuitry having one or more processors and a memory storing, or tostore, machine-executable instructions which, when executed by the oneor more processors, control the one or more processors to: a) cause theselector valve to select between a set of reagent sippers associatedwith reagents to be pre-mixed, b) cause the pump to aspirate fluid fromeach of the selected reagent sippers and to deliver the fluids aspiratedfrom the corresponding selected reagent sippers one-by-one into themixing volume, c) cause the pump to dispense the aspirated fluids in themixing volume resulting from (b) through a destination recipient sipper,and d) cause the pump to cyclically move the aspirated fluids into andout of the mixing volume and through the destination recipient sipper tofurther mix the fluids.

In some such implementations, the mixing volume may include or be in theform of a serpentine channel.

In some implementations of the system, the system may further include adestination recipient positioned to receive fluids ejected through thedestination recipient sipper; the destination recipient may contain DNAto be sequenced.

In some implementations of the system, the pump may be or include asyringe pump.

In some implementations of the system, the selector valve may permit thepump to aspirate air into the mixing volume prior to delivering thefluids from the selected reagent sippers into the mixing volume.

In some implementations of the system, the memory may store, or be tostore, further machine-executable instructions which, when executed bythe one or more processors, further control the one or more processorsto cause the pump to cyclically move the aspirated fluids into and outof the mixing volume while maintaining a volume of air trapped betweenthe pump and the fluids.

In some implementations of the system, the memory may store, or be tostore, further machine-executable instructions which, when executed bythe one or more processors, further control the one or more processorsto cause (b) to be repeated one or more times prior to the performanceof (c) or (d) for the analysis operation.

In some such implementations of the system, the memory may store, or beto store, further machine-executable instructions which, when executedby the one or more processors, further control the one or moreprocessors to: (e) cause the selector valve to select an additionalreagent sipper associated with an additional reagent, (f) cause the pumpto aspirate fluid from the additional reagent sipper, and (g) cause thepump to deliver the aspirated additional fluid from the additionalreagent sipper into the mixing volume, wherein the additional reagentsipper is not in the set of reagent sippers from (a) and wherein (e)-(g)are performed in between (b) and (c).

In some implementations of the system, the system may further includereagent recipients containing at least three reagents of differentspecific gravities that are to be pre-mixed.

In some implementations, a method may be provided that includes (a)performing a reagent pre-mixing operation for two or more reagents, b)actuating the pump to cyclically move the aspirated reagents into andout of the mixing volume to mix the reagents, and c) actuating the pumpto eject the mixed reagents into a destination recipient. The reagentpre-mixing operation of (a) may include: commanding a selector valve toselect a first reagent, actuating a pump to aspirate a portion of thefirst reagent from a first recipient into a mixing volume, commandingthe selector valve to select a second reagent, and actuating the pump toaspirate a portion of the second reagent from a second recipient intothe mixing volume.

In some implementations of the method, the mixing volume may include orbe a serpentine channel.

In some implementations of the method, the destination recipient maycontain DNA to be sequenced.

In some implementations of the method, the reagent pre-mixing operationof (a) may further include commanding the selector valve to select athird reagent and actuating the pump to aspirate a portion of the thirdreagent from a third recipient into the mixing volume.

In some such implementations of the method, the reagent pre-mixingoperation of (a) may further include selecting and aspirating at leastone of the reagents more than once prior to performing (b). In some suchimplementations of the method, the pre-mixing operation of (a) may berepeated one or more times prior to performing (b).

In some implementations of the method, the method may further includeaspirating air into the mixing volume prior to aspirating the firstreagent.

In some implementations, a method may be provided that includesactuating a pump to aspirate a gas into a mixing volume; controlling aselector valve to select, one-by-one, a plurality of liquid reagents foran analysis operation; actuating, for each selected reagent, a pump toaspirate the selected reagent from a respective recipient containing theselected reagent into a serpentine mixing volume; controlling theselector valve to fluidically connect the serpentine mixing volume witha destination recipient; cycling the pump to move the reagents back andforth between the serpentine mixing volume and a destination recipientto mix the reagents, wherein the destination recipient contains ananalyte of interest to be analyzed in the analysis operation; andactuating the pump to eject the mixed reagents into the destinationrecipient.

In some implementations of such a method, the method may further includeselecting and aspirating each reagent more than once prior to cyclingthe pump to move the reagents.

In some implementations of such a method, the pump may be used tocyclically move the reagents with a volume of air between the pump andthe reagents.

In some implementations of such a method, the reagents may include atleast three reagents of different specific gravities.

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims. Note thatthe relative dimensions of the following figures may not be drawn toscale.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a diagrammatical overview of an example sequencing system inwhich the disclosed techniques may be employed;

FIG. 2 is a diagrammatical overview of an example fluidic system of thesequencing system of FIG. 1;

FIG. 3 is a diagrammatical overview of an example processing and controlsystem of the sequencing system of FIG. 1;

FIG. 4 is a perspective view of an example of a reagent manifold withselector valves;

FIG. 5 is a top view of the example manifold and valve arrangement ofFIG. 4;

FIG. 6A is a diagrammatical view of an example arrangement foraspirating and mixing reagents and a sample template, while FIG. 6Bshow, in one example, how reagents and a sample template would bestriated prior to mixing;

FIG. 7 is a diagrammatical view of an example of how reagents to bemixed may be aspirated individually into a mixing volume;

FIG. 8 is a diagrammatical section of an example destination recipientvessel for mixed reagent and a sample template showing a nozzle sipperejecting mixed reagents into the recipient;

FIGS. 9A-9D illustrate an example nozzle sipper that may be used in themixing of the reagents;

FIG. 10 is a graphical representation of example cycles in aspiratingand mixing reagents and a sample template; and

FIG. 11 is a flow chart illustrating example logic for aspirating andmixing reagents and a sample template.

DETAILED DESCRIPTION

FIG. 1 illustrates an implementation of a sequencing system 10configured to process molecular samples that may be sequenced todetermine their components, the component ordering, and generally thestructure of the sample. The system includes an instrument 12 thatreceives and processes a biological sample. A sample source 14 providesthe sample 16 which in many cases will include a tissue sample. Thesample source may include, for example, an individual or subject, suchas a human, animal, microorganism, plant, or other donor (includingenvironmental samples), or any other subject that includes organicmolecules of interest, the sequence of which is to be determined. Thesystem may be used with samples other than those taken from organisms,including synthesized molecules. In many cases, the molecules willinclude DNA, RNA, or other molecules having base pairs the sequence ofwhich may define genes and variants having particular functions ofultimate interest.

The sample 16 is introduced into a sample/library preparation system 18.This system may isolate, break, and otherwise prepare the sample foranalysis. The resulting library includes the molecules of interest inlengths that facilitate the sequencing operation. The resulting libraryis then provided to the instrument 12 where the sequencing operation isperformed. In practice, the library, which may sometimes be referred toas a template, is combined with reagents in an automated orsemi-automated process, and then introduced to the flow cell prior tosequencing. In some such implementations, the library may be pre-mixedwith reagents before being routed to the flow cell, e.g., the librarymay be routed through a selector valve system, such as is describedbelow, and mixed with reagents in a destination recipient before beingtransferred to the flow cell.

In the implementation illustrated in FIG. 1, the instrument includes aflow cell or array 20 that receives the sample library. The flow cellincludes one or more fluidic channels that allow for sequencingchemistry to occur, including attachment of the molecules of thelibrary, and amplification at locations or sites that can be detectedduring the sequencing operation. For example, the flow cell/array 20 mayinclude sequencing templates immobilized on one or more surfaces at thelocations or sites. A “flow cell” may include a patterned array, such asa microarray, a nanoarray, and so forth. In practice, the locations orsites may be disposed in a regular, repeating pattern, a complexnon-repeating pattern, or in a random arrangement on one or moresurfaces of a support. To enable the sequencing chemistry to occur, theflow cell also allows for introduction of substances, such as includingvarious reagents, buffers, and other reaction media, that are used forreactions, flushing, and so forth. The substances flow through the flowcell and may contact the molecules of interest at the individual sites.

In the instrument the flow cell 20 is mounted on a movable stage 22that, in this implementation, may be moved in one or more directions asindicated by reference numeral 24. The flow cell 20 may, for example, beprovided in the form of a removable and replaceable cartridge that mayinterface with ports on the movable stage 22 or other components of thesystem in order to allow reagents and other fluids to be delivered to orfrom the flow cell 20. The stage is associated with an optical detectionsystem 26 that can direct radiation or light 28 to the flow cell duringsequencing. The optical detection system may employ various methods,such as fluorescence microscopy methods, for detection of the analytesdisposed at the sites of the flow cell. By way of a non-limitingexample, the optical detection system 26 may employ confocal linescanning to produce progressive pixilated image data that can beanalyzed to locate individual sites in the flow cell and to determinethe type of nucleotide that was most recently attached or bound to eachsite. Other suitable imaging techniques may also be employed, such astechniques in which one or more points of radiation are scanned alongthe sample or techniques employing “step and shoot” imaging approaches.The optical detection system 26 and the stage 22 may cooperate tomaintain the flow cell and detection system in a static relationshipwhile obtaining an area image, or, as noted, the flow cell may bescanned in any suitable mode (e.g., point scanning, line scanning,“step-and-shoot” scanning).

While many different technologies may be used for imaging, or moregenerally for detecting the molecules at the sites, presentlycontemplated implementations may make use of confocal optical imaging atwavelengths that cause excitation of fluorescent tags. The tags, excitedby virtue of their absorption spectrum, return fluorescent signals byvirtue of their emission spectrum. The optical detection system 26 isconfigured to capture such signals, to process pixelated image data at aresolution that allows for analysis of the signal-emitting sites, and toprocess and store the resulting image data (or data derived from it).

In a sequencing operation, cyclic operations or processes areimplemented in an automated or semi-automated fashion in which reactionsare promoted, such as with single nucleotides or with oligonucleotides,followed by flushing, imaging and de-blocking in preparation for asubsequent cycle. The sample library, prepared for sequencing andimmobilized on the flow cell, may undergo a number of such cycles beforeall useful information is extracted from the library. The opticaldetection system may generate image data from scans of the flow cell(and its sites) during each cycle of the sequencing operation by use ofelectronic detection circuits (e.g., cameras or imaging electroniccircuits or chips). The resulting image data may then be analyzed tolocate individual sites in the image data, and to analyze andcharacterize the molecules present at the sites, such as by reference toa specific color or wavelength of light (a characteristic emissionspectrum of a particular fluorescent tag) that is detected at a specificlocation, as indicated by a group or cluster of pixels in the image dataat the location. In a DNA or RNA sequencing application, for example,the four common nucleotides may be represented by distinguishablefluorescence emission spectra (wavelengths or wavelength ranges oflight). Each emission spectrum, then, may be assigned a valuecorresponding to that nucleotide. Based upon this analysis, and trackingthe cyclical values determined for each site, individual nucleotides andtheir orders may be determined for each site. These sequences may thenbe further processed to assemble longer segments including genes,chromosomes, and so forth. As used in this disclosure the terms“automated” and “semi-automated” mean that the operations are performedby system programming or configuration with little or no humaninteraction once the operations are initiated, or once processesincluding the operations are initiated.

In the illustrated implementation, reagents 30 are drawn or aspiratedinto the flow cell through valving 32. The valving may access thereagents from recipients or vessels in which they are stored, such asthrough pipettes or sippers (not shown in FIG. 1). The valving 32 mayallow for selection of the reagents based upon a prescribed sequence ofoperations performed. The valving may further receive commands fordirecting the reagents through flow paths 34 into the flow cell 20. Exitor effluent flow paths 36 direct the used reagents from the flow cell.In the illustrated implementation, a pump 38 serves to move the reagentsthrough the system. The pump may also serve other useful functions, suchas measuring reagents or other fluids through the system, aspirating airor other fluids, and so forth. Additional valving 40 downstream of pump38 allows for appropriately directing the used reagent to disposalvessels or recipients 42.

The instrument further includes a range of circuitry that aids incommanding the operation of the various system components, monitoringtheir operation by feedback from sensors, collecting image data, and atleast partially processing the image data. In the implementationillustrated in FIG. 1, a control/supervisory system 44 includes acontrol system 46 and a data acquisition and analysis system 48. Bothsystems will include one or more processors (e.g., digital processingcircuits, such as microprocessors, multi-core processors, FPGA's, or anyother suitable processing circuitry) and associated memory circuitry 50(e.g., solid state memory devices, dynamic memory devices, on and/oroff-board memory devices, and so forth) that may storemachine-executable instructions for controlling, for example, one ormore computers, processors, or other similar logical devices to providecertain functionality. Application-specific or general purpose computersmay at least partially make up the control system and the dataacquisition and analysis system. The control system may include, forexample, circuitry configured (e.g., programmed) to process commands forfluidics, optics, stage control, and any other useful functions of theinstrument. The data acquisition and analysis system 48 interfaces withthe optical detection system to command movement of the opticaldetection system or the stage, or both, the emission of light for cyclicdetection, receiving and processing of returned signals, and so forth.The instrument may also include various interfaces as indicated atreference 52, such as an operator interface that permits control andmonitoring of the instrument, transfer of samples, launching ofautomated or semi-automated sequencing operations, generation ofreports, and so forth. Finally, in the implementation of FIG. 1,external networks or systems 54 maybe coupled to and cooperate with theinstrument, for example, for analysis, control, monitoring, servicing,and other operations.

It may be noted that while a single flow cell and fluidics path, and asingle optical detection system are illustrated in FIG. 1, in someinstruments more than one flow cell and fluidics path may beaccommodated. For example, in a presently contemplated implementation,two such arrangements are provided to enhance sequencing and throughput.In practice, any number of flow cells and paths may be provided. Thesemay make use of the same or different reagent receptacles, disposalreceptacles, control systems, image analysis systems, and so forth.Where provided, the multiple fluidics systems may be individuallycontrolled or controlled in a coordinated fashion. It is to beunderstood that the phrase “fluidically connected” may be used herein todescribe connections between two or more components that place suchcomponents in fluidic communication with one another, much in the samemanner that “electrically connected” may be used to describe anelectrical connection between two or more components. The phrase“fluidically interposed” may be used, for example, to describe aparticular ordering of components. For example, if component B isfluidically interposed between components A and C, then fluid flowingfrom component A to component C would flow through component B beforereaching component C.

FIG. 2 illustrates an example fluidic system of the sequencing system ofFIG. 1. In the implementation illustrated, the flow cell 20 includes aseries of pathways or lanes 56A and 56B which may be grouped in pairsfor receiving fluid substances (e.g., reagents, buffers, reaction media)during sequencing operations. The lanes 56A are coupled to a common line58 (a first common line), while the lanes 56B are coupled to a secondcommon line 60. A bypass line 62 is also provided to allow fluids tobypass the flow cell without entering it. As noted above, a series ofvessels or recipients 64 allow for the storage of reagents and otherfluids that may be utilized during the sequencing operation. A reagentselector valve 66 is mechanically coupled to a motor or actuator (notshown) to allow selection of one or more of the reagents to beintroduced into the flow cell. Selected reagents are then advanced to acommon line selector valve 68 which similarly includes a motor (notshown). The common line selector valve may be commanded to select one ormore of the common lines 58 and 60, or both common lines, to cause thereagents 64 to flow to the lanes 56A and/or 56B in a controlled fashion,or the bypass line 62 to flow one or more of the reagents through thebypass line. It may be noted that other useful operations may be enabledby the bypass line, such as the ability to prime all reagents (andliquids) to the reagent selector valve (and the common line selectorvalve) without drawing air through the flow cell, the ability to performwashing (e.g., automated or semi-automated washing) of the reagentchannels and sippers independent of the flow cell, and the ability toperform diagnostic functions (e.g., pressure and volume delivery tests)on the system.

Used reagents exit the flow cell through lines coupled between the flowcell and the pump 38. In the illustrated implementation, the pumpincludes a syringe pump having a pair of syringes 70 that are controlledand moved by an actuator 72 to aspirate the reagents and other fluidsand to eject the reagents and fluids during different operations of thetesting, verification and sequencing cycles. The pump assembly mayinclude various other parts and components, including valving,instrumentation, actuators, and so forth (not shown). In the illustratedimplementation, pressure sensors 74A and 74B sense pressure on inletlines of the pump, while a pressure sensor 74C is provided to sensepressures output by the syringe pump.

Fluids used by the system enter a used reagent selector valve 76 fromthe pump. This valve allows for selection of one of multiple flow pathsfor used reagents and other fluids. In the illustrated implementation, afirst flow path leads to a first used reagent receptacle 78, while asecond flow path leads through a flow meter 80 a second used reagentreceptacle 82. Depending upon the reagents used, it may be advantageousto collect the reagents, or certain of the reagents in separate vesselsfor disposal, and the used reagent selector valve 76 allows for suchcontrol.

It should be noted that valving within the pump assembly may allow forvarious fluids, including reagents, solvents, cleaners, air, and soforth to be aspirated by the pump and injected or circulated through oneor more of the common lines, the bypass line, and the flow cell.Moreover, as noted above, in a presently contemplated implementation,two parallel implementations of the fluidics system shown in FIG. 2 areprovided under common control. Each of the fluidics systems may be partof a single sequencing instrument, and may carry out functions includingsequencing operations on different flow cells and sample libraries inparallel.

The fluidics system operates under the command of control system 46which implements prescribed protocols for testing, verification,sequencing, and so forth. The prescribed protocols will be establishedin advance and include a series of events or operations for activitiessuch as aspirating reagents, aspirating air, aspirating other fluids,ejecting such reagents, air and fluids, and so forth. The protocols willallow for coordination of such fluidic operations with other operationsof the instrument, such as reactions occurring in the flow cell, imagingof the flow cell and its sites, and so forth. In the illustratedimplementation, the control system 46 employs one or more valveinterfaces 84 which are configured to provide command signals for thevalves, as well as a pump interface 86 configured to command operationof the pump actuator. Various input/output circuits 88 may also beprovided for receiving feedback and processing such feedback, such asfrom the pressure sensors 74A-C and flow meter 80.

FIG. 3 illustrates certain functional components of thecontrol/supervisory system 44. As illustrated, the memory circuitry 50stores prescribed routines that are executed during testing,commissioning, troubleshooting, servicing, and sequencing operations.Many such protocols and routines may be implemented and stored in thememory circuitry, and these may be updated or altered from time to time.As illustrated in FIG. 3, these may include a fluidics control protocol90 for controlling the various valves, pumps, and any other fluidicsactuators, as well as for receiving and processing feedback fromfluidics sensors, such as valves, and flow and pressure sensors. A stagecontrol protocol 92 allows for moving the flow cell as desired, such asduring imaging. An optics control protocol 94 allows for commands to beissued to the imaging components to illuminate portions of the flow celland to receive returned signals for processing. An image acquisition andprocessing protocol 96 allows for the image data to be at leastpartially processed for extraction of useful data for sequencing. Otherprotocols and routines may be provided in the same or different memorycircuitry as indicated by reference 98. In practice, the memorycircuitry may be provided as one or more memory devices, such as bothvolatile and non-volatile memories. This memory may be within theinstrument, and some may be off-board.

One or more processors 100 access the stored protocols and implementthem on the instrument. As noted above, the processing circuitry may bepart of application-specific computers, general-purpose computers, orany suitable hardware, firmware and software platform. The processorsand the operation of the instrument may be commanded by human operatorsvia an operator interface 101. The operator interface may allow fortesting, commissioning, troubleshooting, and servicing, as well as forreporting any issues that may arise in the instrument. The operatorinterface may also allow for launching and monitoring sequencingoperations.

FIG. 4 illustrates a valve assembly that serves to draw reagents andother fluids from recipients and deliver them to the flow cell. Thevalve assembly 102 includes a manifold structure 104 in which channelsare formed to define flow paths for the reagents and other fluids. Ascan be seen in FIG. 4, the valves 66 and 68 are driven and controlled bymotors 106 and 108. One or more motor interfaces or connections 110provide power and, where desired, signals to and from the motors. Asnoted above, the motors (and thereby the valves) are controlled by thecontrol circuitry during testing, commissioning, and servicing, as wellas during the sequencing operation.

The reagent and fluid pathways within the manifold are coupled tosippers 112 that, during operation, draw reagents and other fluids fromrespective recipients (not shown). The flow paths for the reagents andfluids, designated generally by reference 114 in FIG. 4, may be formedby molding, etching, or any other suitable process to allow the reagentsand fluids to move from the sippers to the valves when the pumpdiscussed above is commanded to aspirate the reagents and fluids. Atleast one of the sippers is configured as a nozzle sipper 116 to assistin mixing of reagents during the sequencing operation (e.g., prior toreactions and imaging). Also illustrated in FIG. 4 is a mixing volumeconfigured as a channel 118 in which reagents and fluids can be drawnand moved for mixing. In some implementations, the mixing volume may bea portion or all of the bypass line 62. For example, reagents may beaspirated into the bypass line 62 in a desired sequence but such thatthe reagents do not traverse the entire length of the bypass line (whichmay cause them to be routed to disposal). Once the bypass line (or aportion thereof serving as the mixing volume) has been loaded with thedesired sequence of reagents, the end of the bypass line through whichthe reagents were introduced may be switched, using a valve, so as tofluidically connect with a flow path leading to, for example, adestination recipient so that the entire set of reagents loaded into thebypass line may then be expelled back out of the bypass line and intothe destination recipient. In other implementations, the mixing volumemay, for example, be a destination recipient, e.g., the destinationrecipient from to which the pre-mixed fluids are delivered, or aseparate destination recipient, e.g., one that is completely empty priorto delivery of the selected reagents.

FIG. 5 is a top view of the valve assembly 102. Here again, the valves66 and 68 are visible in the manifold and coupled to the flow paths forthe reagents and fluids. The reagent selector valve 66 receives thereagents from the sippers, and directs the aspirated fluids to thecommon line selector valve 68. The mixing channel 118 is coupled to thecommon line selector valve to allow for mixing of reagents as describedbelow. Also shown in FIG. 5 are ports 120 provided in the manifold toallow for coupling the manifold to the sippers. One of the ports 120(indicated by reference 122) will be coupled to the nozzle sipper toallow for injection of reagents into a destination recipient, and fordrawing the reagents from the destination recipient for mixing. Thedestination recipient, for example, may be a container, tube, or othervessel designed to contain the reagents. The destination recipient may,for example, be used as a temporary work volume to which reagents and/orother materials may be transferred in order to prepare them fordelivery, e.g., by mixing, to the flow cell. Thus, reagents and otherfluids may, once prepared in the destination recipient, be transferredfrom the destination recipient to the flow cells.

A presently contemplated implementation of the mixing channel 118 andreagent flow paths for mixing is illustrated in FIG. 6A. As noted above,the mixing channel 118 is coupled to the common line selector valve 68,which in turn is coupled to an outlet of the reagent selector valve 66.The mixing channel 118 is also coupled to the pump 38 to allow foraspiration and ejection of reagents and fluids as described below. Inthe implementation illustrated in FIG. 6A, reagent recipient or vessels124, 126, and 128 store reagents 130, 132, and 134, respectively. Afurther or destination recipient 136 stores, in this example, apre-prepared sample template or library 138. For the mixing operationthe reagents 130, 132 and 134 are pre-mixed and then combined with thetemplate 138. To allow such pre-mixing, the reagents are aspiratedone-by-one into the mixing channel 118 through respective flow pathsindicated in FIG. 6A by reference 140. A further flow path 142 allowsthe reagents to be deposited in the destination recipient 136 along withthe template. In the illustrated implementation, the mixing channel 118forms a serpentine internal volume having loops 144 that allow for thedesired volumes of reagents to be aspirated and mixed in a relativelycompact area of the manifold.

In a presently contemplated implementation, the reagents 130, 132, and134 have different fluid properties that pose challenges to the mixing.For example, the densities of the reagents differ, and substantialdifferences may exist between the viscosities and oil interfacialtensions of the reagents. In a presently contemplated implementation,for example, the viscosities vary between approximately 1.5 cP and 50cP, e.g., 2.4 cP, at 25° C., while oil interfacial tensions vary betweenabout 5.0 and about 19.2 dynes/cm. The template, by comparison, may havea still different density and a lower viscosity (e.g., on the order of 1cP at 25° C.) and a different oil interfacial tension (e.g., on theorder of about 9.8 dynes/cm). FIG. 6B illustrates striation of thereagents and template in the destination recipient 136 when not mixed.In the illustrated implementation, the template comprises about 30% ofthe total volume, while reagent 130 comprises about 22%, reagent 132comprises about 42%, and reagent 134 comprises about 6%. In the presentcontext, the term “about” is intended to mean that the values indicatedare not exact and the actual value may vary from those indicated in amanner that does not materially alter the operation concerned.

To permit automated mixing of the reagents and template, the fluidicssystem and its control allow for the reagents to be selectivelyaspirated one-by-one into the mixing channel, injected into thedestination recipient, and cyclically withdrawn and re-injected formixing. FIG. 7 illustrates a presently contemplated technique for thereagent aspiration. As shown, the reagents 130, 132, and 134 areaspirated one-by-one by control of valve 66. With the common lineselector valve directing the reagents to the mixing channel, severalsets of volumes of each reagent are aspirated as indicated by referencenumerals 146, 148, 150, 152, and 154. To provide for reduction ofpressure spikes during mixing, the pump may also aspirate a volume ofair prior to aspirating the reagents. The air volume provides a cushionthat limits positive and negative pressure spikes during mixing. In theimplementation illustrated in FIG. 7, the aspirated air would be locatedto the upper left of the reagent sets. Moreover, a liquid buffer may beaspirated that aids in priming, washing, and pushing the reagents. Onceaspirated as illustrated in FIG. 7, the valving can be then controlledto allow the pump to inject the reagents into the template 138 whichwill be pre-loaded into the template recipient 136 described above,i.e., one or both selector valves may be controlled to fluidicallyconnect the mixing volume or mixing channel, e.g., a serpentine mixingchannel, with a destination recipient.

In another technique in which three or more reagents may be selected formixing in the destination recipient, at least two of the reagentsselected for mixing may be repeatedly introduced one-by-one into themixing channel, with at least one other reagent selected for mixingbeing held in reserve until the reagents that are repeatedly introducedone-by-one to the mixing channel have been fully delivered to the mixingchannel. The reserved reagent may then be added all at once to themixing channel. For example, if reagents A and B are to be repeatedlyintroduced one-by-one into the mixing channel, followed by reservedreagent C, then the reagents in the mixing channel would generally belayered as ABABABABABC, as opposed to ABCABCABCABCABC (which wouldresult from, for example, a technique similar to that discussed withrespect to FIG. 7). Such a technique is believed to be advantageous inpreventing or reducing the occurrence of, for some reagents, undesiredreaction byproducts. For example, the reserved reagent may react withone of the other reagents in isolation in one particular manner, but mayreact with two or more of the other reagents in combination in anothermanner. The latter may be the desired reaction that may occur once thereagents have been thoroughly mixed, whereas the former may occur duringpre-mixing when the reagents may still be relatively stratified and mayonly mix with the directly adjacent neighboring reagent. In anotherexample, the reserved reagent may react with the material that forms thestructure of the mixing channel and produce an undesired byproduct.Since the repeated one-by-one introduction of reagents to the mixingchannel may require several minutes, e.g., 5 minutes, 10 minutes, 15minutes, or longer, depending on the number and quantity of each reagentdesired, reserving the introduction of potentially troublesome reagentsuntil after the other reagents have been delivered one-by-one to themixing channel may significantly reduce the amount of time that thereserved reagent spends in contact with the other reagents and with thestructure of the mixing channel, thereby reducing the potential forundesirable reaction byproducts to be generated. Of course, in suchimplementations, the reserved reagent may not benefit from thepre-mixing that the other reagents benefit from, but the reducedpotential for undesirable reaction byproducts may outweigh the loss ofthe pre-mixing with respect to the reserved reagent. In particular, ifthe reserved reagent is a lower-viscosity liquid, the loss of pre-mixingwith respect to the reserved agent may ultimately have little impact.

The use of a channel-like mixing volume, e.g., a volume that is muchlonger in length than it is wide (for example, at least 10×, 100×, 150×to 170×, 160×, 200×, or 500× longer than it is wide) may allow theserially-delivered reagents to maintain a relatively stratifiedarrangement relative to one another within the channel by reducing thesurface-to-surface contact interface area between each layer of reagents(the reagents are liquid and will thus likely diffuse into each otheracross this boundary to some extent over time, so the boundary/contactinterface areas referenced herein are to be understood to be theoreticalin nature; reducing these theoretical areas will, however, slow the rateof diffusion). In addition, for reagents that may be somewhat immisciblewith one another, a mixing volume that is, for example, spherical inshape or that has a larger width-to-length ratio may allow the variousreagent doses that are delivered into the mixing volume to float withinthe mixing volume and potentially re-combine with earlier doses of thatsame reagent, thereby losing the stratification that may be achieved ina channel-like mixing volume. For example, a mixing channel that isapproximately 2.25 mm in diameter or width for approximately 360 mm ofits length may provide advantageous stratification in delivered reagentsduring the pre-mixing process. Once the mixing volume has been loadedwith the desired quantities of the multiple sets of reagents, thecontents of the mixing volume may be delivered to the destinationrecipient (some portion of the fluids in the mixing volume may be lostto the dead volume of the fluidic system; the total volume of thereagents delivered to the mixing volume may be calibrated to account forsuch loss). After delivery to the destination recipient, the deliveredpre-mixed reagents may be repeatedly aspirated from and ejected backinto the destination recipient to promote further mixing. In someimplementations, the pre-mixed (or post-pre-mixed) reagents may beaspirated from the destination recipient and pulled back into the mixingvolume before being ejected back into the destination recipient. Thus,in such implementations, the pre-mixed reagents may be moved into andout of the mixing volume repeatedly during the aspiration/ejectionmixing operation.

It has been found that the use of the mixing channel with a nozzlesipper that promotes vorticity in the destination recipient and providesexcellent mixing of reagents and the template despite substantialdifferences in fluid properties of the reagents. Moreover, thesestructures and techniques enable automated mixing with little or nohuman interaction. An example nozzle sipper for use in these techniquesis illustrated an FIGS. 8 and 9A-9C. As shown in FIG. 8, the nozzlesipper has an elongated body with a central lumen (cavity) extendingalong its length and a tip 156 at its distal end. A nozzle is providedat the tip to reduce the inner diameter of the sipper at this locationto increase the velocity of fluids aspirated and ejected through thesipper. In the illustrated implementation, the nozzle is formed as aninsert 158 that is lodged in the distal end or tip of the sipper. Otherstructures, such as caps, machined, formed, upset regions, and so forthcould form the nozzle.

In the illustrated implementation, the sipper as a nominal outerdiameter 160 of about 0.125 inches (3.175 mm), and a nominal innerdiameter 162 of 0.020 inches±0.001 inches (0.508 mm). The nozzle, on theother hand, as a nominal inner diameter 164 of 0.010 inches±0.001 inches(0.254 mm, although some implementations may feature a nozzle innerdiameter ranging up to between 0.20 and 0.28 mm). Of course, other sizesand dimensions may be utilized to provide the desired mixing. Further,in the illustrated implementation, the nozzle sipper 116 is positionedat a height 166 above the bottom of the recipient 138 of approximately 2mm. As the reagents are injected into the recipient, then, as indicatedby reference 168, vorticity within the recipient is enhanced by virtueof the increased velocity of the reagents moving through the nozzle,thereby enhancing mixing in the recipient, as indicated by arrows 170 inFIG. 8. The mixed reagents are allowed to rise in the recipient asindicated by reference 172.

FIG. 9A illustrates the distal end of the nozzle sipper in somewhatgreater detail. As can be seen in the figure, the nominal inner diameter162 of the sipper is reduced by the nozzle insert 158, in this case toapproximately one half of the inner diameter of the sipper (the nozzleinsert, in this example, is tubular in shape). A presently contemplatedform of the distal end is best illustrated in FIGS. 9B, 9C and 9D. Asshown here, the nozzle sipper has a faceted lower extremity comprisingfour facets 174, giving the appearance of a wedged shape to the nozzlesipper tip. The sipper has a centerline 176, and the facets meet in anapex 178 that is offset or eccentric with respect to the centerline 176.This geometry of the distal end reduces or avoids dragging or scrapingof the recipient as the sipper is lowered into the recipient, or as therecipient is raised around the sipper. It may be noted, however, that inthe illustrated implementation, the insert has a lower contour thatmatches the contour of the tip (e.g., one or more of the angled facets).Put another way, the insert may be shape-compliant with the faceted orthe wedged shape of the distal end of the nozzle sipper. Moreover, itmay be noted that in a presently contemplated implementation the sipperand nozzle are made of an engineering plastic, such aspolyetheretherketone (PEEK). Such materials may provide chemicalresistance to the reagents and any solvents used in the process.

FIG. 10 is a graphical representation of example cycles in aspirating,mixing and ejecting reagents and a sample template, while FIG. 11 is aflow chart illustrating example logic for aspirating and mixing reagentsand a sample template. In FIG. 10, the aspiration, mixing, and ejectioncycle is designated by reference numeral 180, with pressures applied bythe pump indicated by axis 182 and times of the cycle by axis 184.Negative pressures indicate aspiration of one or more of the reagents,while positive pressures indicate ejection. The process may beconsidered to include a “transfer” sequence 186, followed by a “mixing”sequence 196, as discussed below.

Following the flow chart of FIG. 11, the control logic 204 may beginwith aspirating air at 206 to remove existing liquid from flow pathsthrough which previous mixtures of reagents may have been routed. Forexample, any leftover liquid remaining in the flow path 142, which linksthe reagent selector valve 66 with the destination recipient 136, may beaspirated with air (i.e., such that the liquid is replaced with air) sothat any new mixture of reagents that is subsequently delivered to thedestination recipient via the flow path 142 is not comingled with theleftover liquid. The transfer sequence may then begin with a primingsequence as indicated by reference 208 in FIG. 11. This priming sequenceis indicated by the series of negative pressure or aspiration eventscollectively indicated by reference 188 in FIG. 10. In general, theseevents allow for drawing the reagents initially into the system. Insomewhat greater detail, returning to FIG. 11, a buffer may be aspiratedas indicated at 210. This buffer may comprise a liquid selected so as tobe non-reactive or relatively inert with respect to the reagents and maybe used as an incompressible working fluid that extends, at least inpart, between the pump and the reagents to allow for more precisemetering of the reagents into the mixing volume in the following steps,if desired. The first reagent may then be aspirated in a priming eventas indicated at 212 in FIG. 11, followed by aspiration of any number ofother reagents, through the aspiration of the final reagent at 214. In apresently contemplated implementation, for example, three such reagentsare aspirated in the priming sequence.

In the logic illustrated in FIG. 11, the reagents to be mixed are thenaspirated in a transfer sequence 218. The transfer sequence continueswith aspiration of the first reagent as indicated at 220, followed byaspiration, one-by-one, of each of the additional reagents until thefinal reagent is aspirated as indicated at 222. As before, in apresently contemplated implementation three reagents are aspirated inthis sequence. As noted above, in a presently contemplatedimplementation a number of sets of the reagents are aspirated inrelatively small quantities to create a sequence of the reagents, andthereby to promote pre-mixing. Thus, at 224 the logic may determinewhether all sets of the reagents have been aspirated, and if not, returnto 220 to continue aspirating additional sets. It may also be noted thatin the presently contemplated implementation all sets contain allreagents selected for mixing, although this need not be the case.Moreover, different volumes or quantities of reagents could be aspiratedin the various sets. Once all of the reagents have an aspirated, controlmay advance beyond the transfer sequence. The transfer sequence isillustrated by the negative pressure events collectively indicated byreference numeral 190 in FIG. 10.

As shown in FIG. 11, and as will be clear from the separate negative(and positive) pressure events of FIG. 10, each successive aspiration(or ejection) of reagents or pre-mixed reagents involves controlling oneor more of the valves described above, as well as the pump. That is, toaspirate the individual reagents, the reagent selector valve will beshifted to direct negative pressure to the sipper for the correspondingrecipient of the selected reagent. The pump will similarly be commandedto draw the reagent (or air or buffer or template), and to express theaspirated fluids in accordance with the prescribed protocol. This mixingprotocol will be predetermined and stored in the memory circuitrydescribed above and carried out in an automated or semi-automatedfashion based upon the sequencing operation, also defined in the memorycircuitry. These protocols are executed by the processing and controlcircuitry which, through appropriate interface circuitry commandsoperation of the valves and pump.

Once all of the reagents have been aspirated, the aspirated fluids maybe ejected into the destination recipient as indicated at 226 in FIG.11. As noted above, in the presently contemplated implementation, thisis done through the nozzle sipper where mixing begins by virtue of theincreased velocity of the reagents through the nozzle and the resultingvorticity in the destination recipient. This ejection into thedestination recipient is indicated by the positive pressure event 192 inFIG. 10. In certain implementations, aspiration may be further performedas indicated at reference 228 in FIG. 11. Thereafter, the aspiratedreagents may be ejected into the destination recipient. This sequencemay be followed by aspiration of air as indicated by reference numeral230 in FIG. 11 and the negative pressure event 194 in FIG. 10 (e.g., toremove as much liquid as possible from the bypass line, mixing channel,template channel, and sipper). It may also be noted that in someimplementations, the nozzle sipper, or the recipient, or both may bemoved with respect to the other (e.g., vertically) during aspiration andejection to further help mix striated samples and reagents.

Following aspiration and partial pre-mixing in the mixing volume orchannel by the operations described above, mixing is performed byrepeatedly moving the reagents in the channel, and between the channeland the destination recipient through the nozzle sipper. For this, aseries of mixing cycles is implemented in a mixing sequence 234. In thissequence, the combined reagents and template are aspirated at 236 andejected back into the destination recipient at 238. The logic mayrepeatedly determine whether all of these desired mixing cycles havebeen performed at 240, and continue until all such cycles are complete.In the graphical illustration of FIG. 10, the cycles are collectivelyindicated by reference 198. As may be seen, each involves a relativelyshort negative pressure event followed by a relatively short positivepressure event. These events effectively aspirate the combined reagentsand template into the mixing volume or channel through the nozzlesipper, and return the progressively mixed reagents and template to thedestination recipient through the nozzle. While any desired volume maybe displaced in this process, in a presently contemplatedimplementation, about 2,000 μL are aspirated from and ejected into thedestination recipient in each mixing cycle, although otherimplementations may dispense about 500 μL or 1500 μL, depending on thesize of the flow cells that are used. At the end of the mixing process,the mixed reagents and template may be returned to the destinationrecipient for proceeding with the sequencing operation.

The use, if any, of ordinal indicators, e.g., (a), (b), (c) . . . or thelike, in this disclosure and claims is to be understood as not conveyingany particular order or sequence, except to the extent that such anorder or sequence is explicitly indicated. For example, if there arethree steps labeled (i), (ii), and (iii), it is to be understood thatthese steps may be performed in any order (or even concurrently, if nototherwise contraindicated) unless indicated otherwise. For example, ifstep (ii) involves the handling of an element that is created in step(i), then step (ii) may be viewed as happening at some point after step(i). Similarly, if step (i) involves the handling of an element that iscreated in step (ii), the reverse is to be understood.

It is also to be understood that the use of “to,” e.g., “a valve toswitch between two flow paths,” may be replaceable with language such as“configured to,” e.g., “a valve configured to switch between two flowpaths”, or the like.

Terms such as “about,” “approximately,” “substantially,” “nominal,” orthe like, when used in reference to quantities or similar quantifiableproperties, are to be understood to be inclusive of values within ±10%of the values specified, unless otherwise indicated.

In addition to the claims listed in this disclosure, the followingadditional implementations are to be understood to be within the scopeof this disclosure:

Implementation 1: A system including: a flow cell to support analytes ofinterest; a selector valve coupled to the flow cell to select aplurality of reagents for an analysis operation; a pump coupled to theflow cell and to a bypass line to displace fluids through the flow cellduring an analysis operation and through the bypass line during areagent mixing operation; a mixing volume in fluid communication withthe bypass line; and control circuitry coupled to the selector valve andto the pump to command the selector valve to select reagents to bemixed, and to command the pump to aspirate the selected reagents fromrespective recipients, one-by-one into the mixing volume, to cyclicallymove the aspirated reagents in the mixing volume to mix the reagents,and to eject the mixed reagents into a destination recipient.

Implementation 2: The system of implementation 1, in which the mixingvolume includes a serpentine channel.

Implementation 3: The system of implementation 1, in which thedestination recipient includes DNA to be sequenced.

Implementation 4: The system of implementation 1, in which the pumpincludes a syringe pump.

Implementation 5: The system of implementation 1, including a valve topermit the pump to aspirate air prior to aspirating the reagents.

Implementation 6: The system of implementation 5, in which the pumpcyclically moves the aspirated reagents with a volume of air between thepump and the aspirated reagents.

Implementation 7: The system of implementation 1, in which the reagentscomprise at least three reagents of different specific gravities.

Implementation 8: A method including: commanding a selector valve toselect a first reagent; actuating a pump to aspirate the first reagentfrom a first recipient into a mixing volume; commanding the selectorvalve to select a second reagent; actuating the pump to aspirate thesecond reagent from a second recipient into the mixing volume; actuatingthe pump to cyclically move the aspirated reagents in the mixing volumeto mix the reagents; and actuating the pump to eject the mixed reagentsinto a destination recipient.

Implementation 9: The method of implementation 8, in which the mixingvolume includes a serpentine channel.

Implementation 10: The method of implementation 8, in which thedestination recipient includes DNA to be sequenced.

Implementation 11: The method of implementation 8, including, prior toactuating the pump to cyclically move the aspirated reagents, commandingthe selector valve to select a third reagent, and actuating the pump toaspirate a third reagent from a third recipient into the mixing volume.

Implementation 12: The method of implementation 11, including selectingand aspirating at least one of the reagents more than once prior toactuating the pump to cyclically move the aspirated reagents.

Implementation 13: The method of implementation 12, including selectingand aspirating all of the reagents more than once prior to actuating thepump to cyclically move the aspirated reagents.

Implementation 14: The method of implementation 8, including aspiratingair into the mixing volume prior to aspirating the first reagent.

Implementation 15: The method of implementation 14, in which the firstreagent is selected to provide a meniscus that avoids ingress of airinto the regents during aspiration or movement in the mixing volume.

Implementation 16: A method including: actuating a pump to aspirate agas into a mixing volume; commanding a selector valve to select,one-by-one, a plurality of reagents for an analysis operation; for eachselected reagent, actuating a pump to aspirate the selected reagent froma respective recipient into a serpentine mixing volume; cycling the pumpto move the reagents in the mixing volume to mix the reagents; andactuating the pump to eject the mixed reagents into a destinationrecipient including an analyte of interest to be analyzed in theanalysis operation.

Implementation 17: The method of implementation 16, including selectingand aspirating each reagent more than once prior to cycling the pump tomove the reagents.

Implementation 18: The method of implementation 17, in which a firstreagent selected and aspirated is selected to provide a meniscus thatavoids ingress of air into the regents during aspiration or movement inthe mixing volume.

Implementation 19: The method of implementation 16, in which the pumpcyclically moves the aspirated reagents with a volume of air between thepump and the aspirated reagents.

Implementation 20: The method of implementation 16, in which thereagents comprise at least three reagents of different specificgravities. It should be appreciated that all combinations of theforegoing concepts (provided such concepts are not mutuallyinconsistent) are contemplated as being part of the inventive subjectmatter disclosed herein. In particular, all combinations of claimedsubject matter appearing at the end of this disclosure are contemplatedas being part of the inventive subject matter disclosed herein. Itshould also be appreciated that terminology explicitly employed hereinthat also may appear in any disclosure incorporated by reference shouldbe accorded a meaning most consistent with the particular conceptsdisclosed herein.

What is claimed is:
 1. A method comprising: a) performing a reagentpre-mixing operation for two or more reagents including: commanding aselector valve to select a first reagent; actuating a pump to aspirate aportion of the first reagent from a first recipient into a mixingvolume; commanding the selector valve to select a second reagent; andactuating the pump to aspirate a portion of the second reagent from asecond recipient into the mixing volume; b) actuating the pump tocyclically move the aspirated reagents into and out of the mixing volumeto mix the reagents; and c) actuating the pump to eject the mixedreagents into a destination recipient.
 2. The method of claim 1, whereinthe mixing volume comprises a serpentine channel.
 3. The method of claim1, wherein the destination recipient contains DNA to be sequenced. 4.The method of claim 1, wherein (a) further comprises commanding theselector valve to select a third reagent and actuating the pump toaspirate a portion of the third reagent from a third recipient into themixing volume.
 5. The method of claim 4, wherein (a) further includesselecting and aspirating at least one of the reagents more than onceprior to performing (b).
 6. The method of claim 5, further comprisingrepeating (a) one or more times prior to performing (b).
 7. The methodof claim 1, comprising aspirating air into the mixing volume prior toaspirating the first reagent.
 8. A method comprising: actuating a pumpto aspirate a gas into a mixing volume; controlling a selector valve toselect, one-by-one, a plurality of liquid reagents for an analysisoperation; for each selected reagent, actuating a pump to aspirate theselected reagent from a respective recipient containing the selectedreagent into a serpentine mixing volume; controlling the selector valveto fluidically connect the serpentine mixing volume with a destinationrecipient; cycling the pump to move the reagents back and forth betweenthe serpentine mixing volume and a destination recipient to mix thereagents, wherein the destination recipient contains an analyte ofinterest to be analyzed in the analysis operation; and actuating thepump to eject the mixed reagents into the destination recipient.
 9. Themethod of claim 8, comprising selecting and aspirating each reagent morethan once prior to cycling the pump to move the reagents.
 10. The methodof claim 8, wherein the pump cyclically moves the reagents with a volumeof air between the pump and the reagents.
 11. The method of claim 8,wherein the reagents comprise at least three reagents of differentspecific gravities.
 12. A method comprising: loading a mixing volumewith a first reagent sequence formed by a first amount of a firstreagent followed by a second amount of a second reagent, wherein loadingthe mixing volume with the first reagent sequence comprises: controllinga selector valve to select the first reagent; actuating a pump toaspirate the first amount of the selected first reagent from a firstrecipient containing the selected first reagent and into the mixingvolume; controlling the selector valve to select the second reagent; andactuating the pump to aspirate the second amount of the selected secondreagent from a second recipient containing the selected second reagentand into the mixing volume; and actuating the pump to eject theaspirated reagents from the mixing volume and into a destinationrecipient.
 13. The method of claim 12, wherein the first reagentsequence further includes a third amount of a third reagent that followsthe second amount of the second reagent and wherein loading the mixingvolume with the first reagent sequence further comprises: controllingthe selector valve to select the third reagent; and actuating the pumpto aspirate the third amount of the selected third reagent from a thirdrecipient containing the selected third reagent into the mixing volume.14. The method of claim 12, wherein loading the mixing volume furthercomprises: loading the mixing volume with a second reagent sequenceformed by a third amount of the first reagent followed by a fourthamount of the second reagent, wherein the second reagent sequencefollows the first reagent sequence.
 15. The method of claim 12, whereinthe destination recipient contains an analyte of interest to beanalyzed.
 16. The method of claim 12, wherein the destination recipientcontains DNA to be sequenced.
 17. The method of claim 12, furthercomprising actuating the pump to cyclically move the aspirated reagentsinto and out of the mixing volume to mix the aspirated reagents.
 18. Themethod of claim 12 further comprising cycling the pump to move theaspirated reagents back and forth between the mixing volume and thedestination recipient to mix the aspirated reagents.
 19. The method ofclaim 12 further comprising actuating the pump to aspirate a gas intothe mixing volume, the gas being fluidically interposed between the pumpand the aspirated reagents.
 20. The method of claim 12, wherein loadingthe mixing volume comprises loading the mixing volume with a pluralityof repetitions of the first reagent sequence.